1. Field of Invention
This invention relates to solar cell conductor formulations made from two silver powders having different particle size distributions, an aluminum powder, and two frit glass compositions having softening points in the range of 250-700° C. and whose softening points differ by at least 10° C. The formulations are pastes dispersed in an organic system. The formulations can fire-through a passivation layer(s), thereby allowing the use of a passivation layer on both sides of a silicon wafer based photovoltaic cell. The formulations are screen-printable and suitable for use in the fabrication of photovoltaic devices, in particular a solar cell with n-type emitter or a metal wrap through (MWT) and emitter wrap through (EWT).
2. Description of Related Art
Solar cells are generally made of semiconductor materials, such as silicon (Si), which convert sunlight into useful electrical energy. A conventional solar cell is in general made of thin p-type Si wafer in which the required PN junction is formed by diffusing phosphorus (P) from a suitable phosphorus source on top of wafer generating the n-type emitter layer. The side of the silicon wafer on which sunlight is incident is generally coated with an anti-reflective coating (ARC) to prevent reflective loss of sunlight. This ARC also passivates the surface which decreases electronic/optical loss due to surface recombination. Low resistance contacts to n-type emitter layers are known. However, a need exists to make low contact resistance contacts to p-type emitters. The inventive pastes are directed towards this need.